In response to the cooling problem of computers that still has accumulated heat energy not being dispelled in a shutdown condition, R.O.C. patent publication No. 392106 discloses a technique which outputs a fan switch control signal through a south bridge chip set that passes through a control circuit to a fan power switch and a switch circuit to switch power supply of a cooling fan in the shutdown condition. R.O.C. patent publication No. 400968 discloses a power supply that has a non-stop power system, a main power supply system and a delay switch device which is electrically connected to a cooling fan that can switch to supply different power to drive the cooling fan when the computer is in an ON or OFF condition. The technique of No. 400968 is mostly adopted in the present market. There are some other techniques developed based on this approach, such as R.O.C. patent publication Nos. 572579 and 568300, and Pat. Nos.